curvature versus slope
  n = 2670057 
  X=0, Y = 21.81 +/- 13.73 
  Weighted least-squares fit:  Y = 53.3 + 2.183 X  + -0.02277 X**2 

slope versus dZ, curvature < 5
  n = 38236 

  Weighted least-squares fit:  Y = 11.2 + 0.407 X  + -0.00129 X**2 
     at X = 100, Y = 38.9 
     effective RMSE xy = 58.6 

slope versus dZ, curvature < 15
  n = 182519 

  Weighted least-squares fit:  Y = 11.8 + 0.533 X  + -0.00136 X**2 

curvature versus dZ, slope < 10
  n = 7587 
  X=0, Y = 11.07 +/- 7.22 
  Weighted least-squares fit:  Y = 10.6 + 1.317 X  + 0.04696 X**2 


Number of samples 2700221
Max dz = 900
Mean dz = 53
RMS dz = 81.859635963
100cm = 85.8050507718 percentile value of dz